Robert von Lieben

Lieben and his associates Eugen Reisz and Siegmund Strauss invented and produced a gas-filled triode – the first thermionic valve with a control grid that was designed specifically for amplification rather than demodulation of signals, and is a distant ancestor of the thyratron.

[2] Robert von Lieben was the fourth of five children born into a wealthy Viennese Jewish family who were related to the Auspitz, Gomperz, Todesco and Wertheimstein clans.

[7] Well before Robert was born,[8] Anna von Lieben suffered from chronic insomnia, drug addiction and various mental conditions.

[15][17] During his two years at Göttingen,[18] Lieben designed a camera for photographing the retina of the eye, an electrolytic phonograph and an electric transmission for vehicles.

[19] Factory engineers Eugen Reisz and Siegmund Strauss assisted Lieben at the laboratory, and Leiser was his main scientific advisor until 1909.

[20] Lieben decided to make a low-distortion electronic amplifier using the already-known cathode ray tube principle to control the flow of current with a weak input signal.

De Forest noted the audion's sensitivity but did not make the conclusion it could amplify signals; this discovery was made almost simultaneously by Lieben and Edwin Howard Armstrong.

[27] Later the same year, Alexander Meissner of Telefunken applied his theory of positive feedback and used the Lieben valve to create a continuous-wave radio transmitter.

Meissner's prototype generated 12 W of output power at a wavelength of 600 metres (about 500 kHz), transmitting amplitude-modulated radiotelephone signals over a range of up to 36 km (22 miles).

According to Reiner zur Linde, it was not an invention but a development of existing designs and ideas of John Ambrose Fleming, Lee de Forest, Arthur Wehnelt and others.

[32] Nevertheless, Linde agreed it is a milestone in telephone technology; Lieben and his associates created the electronic amplifier, a working, low-distortion alternative to the carbon microphone repeater.